Lens tube and imaging system having the same

Abstract

The lens tube includes a cylindrical barrel, a holder, a cap, and a stress applying portion. The barrel houses at least one first lens. The holder houses an imaging element and is fixed to a substrate. The holder is configured to allow one end of the barrel in an axial direction to be screwed into the holder such that an optical axis of the first lens and an optical axis of the imaging element are aligned with each other. The cap is mountable to the barrel by allowing the other end of the barrel in the axial direction to be screwed into the cap. The stress applying portion is located between the holder and the cap when the barrel is screwed into the holder and the cap, and applies a stress in a direction in which the cap is separated from the holder. The first lens is held and fixed between a first stopper formed on the cap and a second stopper formed in the barrel when the cap is mounted to the barrel.

The invention claimed is: 
     
       1. A lens tube comprising:
 a barrel in a cylindrical shape that houses at least one first lens; 
 a holder that houses an imaging element and is fixed to a substrate, the holder being configured to allow one end of the barrel in an axial direction to be screwed into the holder such that an optical axis of the first lens and an optical axis of the imaging element are aligned with each other; 
 a cap that is mountable to the barrel by allowing the other end of the barrel in the axial direction to be screwed into the cap; and 
 a stress applying portion which is located between the holder and the cap when the barrel is screwed into the holder and the cap, and applies a stress in a direction in which the cap is separated from the holder, wherein 
 the first lens is held and fixed between a first stopper formed on the cap and a second stopper formed in the barrel when the cap is mounted to the barrel, and 
 the stress applying portion comprises a biasing member that is configured to bias the cap away from the holder. 
 
     
     
       2. The lens tube according to  claim 1 , wherein
 the stress applying portion applies a uniform stress on the cap about an axis of the barrel. 
 
     
     
       3. The lens tube according to  claim 2 , wherein
 the holder has a first thread that allows the barrel to be screwed into the holder, 
 the cap has a second thread that allows the barrel to be screwed into the cap, and 
 the first thread and the second thread are threaded in the same direction. 
 
     
     
       4. The lens tube according to  claim 2 , wherein
 the cap is formed so as to house at least one second lens, and 
 the second lens is held and fixed between the first stopper and the second stopper along with the first lens when the cap is mounted to the barrel. 
 
     
     
       5. The lens tube according to  claim 2 , wherein
 the first lens includes at least two lenses, and 
 the lens tube further includes a first spacer that maintains a space between the at least two lenses of the first lens. 
 
     
     
       6. The lens tube according to  claim 1 , wherein
 the holder has a first thread that allows the barrel to be screwed into the holder, 
 the cap has a second thread that allows the barrel to be screwed into the cap, and 
 the first thread and the second thread are threaded in the same direction. 
 
     
     
       7. The lens tube according to  claim 6 , wherein
 the cap is formed so as to house at least one second lens, and 
 the second lens is held and fixed between the first stopper and the second stopper along with the first lens when the cap is mounted to the barrel. 
 
     
     
       8. The lens tube according to  claim 6 , wherein
 the first lens includes at least two lenses, and 
 the lens tube further includes a first spacer that maintains a space between the at least two lenses of the first lens. 
 
     
     
       9. The lens tube according to  claim 1 , wherein
 the cap is formed so as to house at least one second lens, and 
 the second lens is held and fixed between the first stopper and the second stopper along with the first lens when the cap is mounted to the barrel. 
 
     
     
       10. The lens tube according to  claim 9 , wherein
 the first lens includes at least two lenses, 
 the lens tube further includes a first spacer that maintains a space between the at least two lenses of the first lens and a second spacer that maintains a space between the first lens and the second lens. 
 
     
     
       11. The lens tube according to  claim 9 , wherein
 the second lens includes at least two lenses, and 
 the lens tube further includes a third spacer that maintains a space between the at least two lenses of the second lens. 
 
     
     
       12. The lens tube according to  claim 10 , wherein
 the second lens includes at least two lenses, and 
 the lens tube further includes a third spacer that maintains a space between the at least two lenses of the second lens. 
 
     
     
       13. The lens tube according to  claim 1 , wherein
 the first lens includes at least two lenses, and 
 the lens tube further includes a first spacer that maintains a space between the at least two lenses of the first lens. 
 
     
     
       14. The lens tube according to  claim 1 , wherein
 the stress applying portion is positioned between an end of the holder and an end of the cap. 
 
     
     
       15. A lens tube comprising:
 a barrel in a cylindrical shape that houses at least one first lens; 
 a holder that houses an imaging element and is fixed to a substrate, the holder being configured to allow one end of the barrel in an axial direction to be screwed into the holder such that an optical axis of the first lens and an optical axis of the imaging element are aligned with each other; 
 a cap that is mountable to the barrel by allowing the other end of the barrel in the axial direction to be screwed into the cap; and 
 a stress applying portion which is located between the holder and the cap when the barrel is screwed into the holder and the cap, and applies a stress in a direction in which the cap is separated from the holder, wherein 
 the first lens is held and fixed between a first stopper formed on the cap and a second stopper formed in the barrel when the cap is mounted to the barrel, and 
 the stress applying portion is formed from an elastic material. 
 
     
     
       16. A lens tube comprising:
 a barrel in a cylindrical shape that houses at least one first lens; 
 a holder that houses an imaging element and is fixed to a substrate, the holder being configured to allow one end of the barrel in an axial direction to be screwed into the holder such that an optical axis of the first lens and an optical axis of the imaging element are aligned with each other; 
 a cap that is mountable to the barrel by allowing the other end of the barrel in the axial direction to be screwed into the cap; and 
 a stress applying portion which is located between the holder and the cap when the barrel is screwed into the holder and the cap, and applies a stress in a direction in which the cap is separated from the holder, wherein 
 the first lens is held and fixed between a first stopper formed on the cap and a second stopper formed in the barrel when the cap is mounted to the barrel, and 
 the stress applying portion has an annular shape and is configured to receive the barrel.